The present invention is directed to bicycles and, more particularly, to various features of an electrically operated bicycle derailleur.
Derailleur operated bicycle transmissions typically comprise a plurality of sprockets that rotate with another rotating member (e.g., the front crank and/or the rear wheel of the bicycle) and a derailleur that is used to shift a chain among the plurality of sprockets. Conventional derailleurs comprise a base member adapted to be mounted to the bicycle frame, a movable member supporting a chain guide, and a linkage mechanism coupled between the base member and the movable member so that the movable member can move laterally inwardly and outwardly relative to the bicycle. Such derailleurs are manually controlled by a hand operated actuator such as a lever or twist-grip attached to the bicycle handlebar, wherein the derailleur is connected to the actuator by a bowden cable.
Recently, various electronic devices have been used to control the movement of the derailleur. Such devices sometimes comprise a traveling condition detector for detecting a traveling condition of the bicycle, a motor for moving the derailleur laterally inwardly and outwardly relative to the plurality of sprockets, and a processor. The processor controls the motor in response to the detected traveling condition so that the derailleur is in the proper position to maintain the traveling condition within a desired range.
The motor used to move the derailleur typically moves the derailleur laterally inwardly and/or laterally outwardly by moving an actuating member such as an actuating arm or a pivot shaft attached to the linkage mechanism. Unfortunately, sometimes the movable member experiences significant resistance to lateral movement, especially when the plurality of sprockets are stationary, and this resistance is communicated to the actuating member. Since the motor may be unable to move the actuating member in such a situation, there is a risk of damage to the motor. Another problem is that an external force may be applied to the movable member such as a force directed toward the wheel when the bicycle lays or falls down, or a force directed away from the wheel if the derailleur catches some external object. Such external forces also may be communicated to the actuating member, thus again risking damage to the motor.